Test and measurement systems are designed to receive signal inputs, e.g. from a Device Under Test (DUT), sample the signals, display the measurement results as well as processed waveforms, and render the waveforms, for example as eye diagrams. Such measurements may include jitter. Jitter is any time deviation of a signal from ideal clean system clocking. Long duration signals may be graphed or rendered by overlaying multiple sweeps of different segments of the signal data in a so called eye diagram. When a signal is rendered in an eye diagram in terms of amplitude versus time, jitter appears as horizontal variance in the signal. Signals may also include Intersymbol Interference (ISI). ISI occurs because changes in a real signal are not perfect because of physical limits such as bandwidth limits of channels. For example, a change in signal value may occur relatively quickly in high speed signaling. However, ripples may be left behind after such a change while the signal settles to a new state. ISI occurs when a ripple from a previous signal state change is present, and interferes with, a subsequent signal state change. When graphed in an eye diagram in terms of amplitude versus time, ISI may appear as a combination of horizontal variance and vertical variance, depending on the signal patterns. Jitter is commonly separated into two categories related to ISI. Correlated jitter is caused by an ISI affect when ISI causes a signal's edge crossing time to change. Uncorrelated jitter is jitter caused by sources other than ISI, such as random jitter and periodic jitter uncorrelated to ISI. ISI correlated jitter may also cause ISI uncorrelated jitter. As both uncorrelated jitter and ISI jitter cause horizontal variance in the signal, a test system may be unable to separate effects of the jitter from effects of ISI in high speed signals.
Examples in the disclosure address these and other issues.